JP7234546B2 - Image forming apparatus and toner patch forming method - Google Patents

Description

The present invention relates to an image forming apparatus that forms a toner image on the surface of a photoreceptor, transfers the toner image to a recording material and outputs the toner image, and a toner patch forming method in the image forming apparatus.

2. Description of the Related Art An image forming apparatus that forms a toner image on a photoreceptor and transfers the toner image to a recording material to output a printout includes a cleaner blade for removing toner remaining on the surface of the photoreceptor. In this type of image forming apparatus, if the friction between the photoreceptor and the cleaner blade increases, the cleaner blade may chip or swell, making it impossible to effectively remove residual toner on the surface of the photoreceptor, resulting in image defects. occurs.

Conventionally, in order to suppress image defects such as those described above, an image patch (toner patch) is formed between the sheets of paper to be conveyed and the next sheet of paper to be conveyed, and a certain amount of toner is applied to the cleaner blade. An image forming apparatus configured to supply is known (for example, Patent Document 1). In this conventional image forming apparatus, the toner amount of the image patch is adjusted according to the coverage rate of the image formed on the paper. When the toner is supplied to the cleaner blade in this way, the friction between the photoreceptor and the cleaner blade is reduced, so that the cleaner blade can be prevented from chipping or sticking.

By the way, in recent image forming apparatuses, the primary transfer rate at which the toner image formed on the photosensitive member is primarily transferred to the intermediate transfer member has been improved, and the primary transfer rate is approaching 100%. Therefore, when a plurality of sheets are continuously conveyed, even if an image patch is formed on the surface of the photoreceptor between the sheets, all the toner forming the image patch is not supplied to the cleaner blade. Instead, a portion of the image patch will be transferred to the intermediate transfer member. In such a situation, the toner of the image patch cannot be sufficiently supplied to the cleaner blade, so the friction between the photoreceptor and the cleaner blade cannot be reduced.

To prevent this, for example, when an image patch is formed between sheets of paper, the intermediate transfer member is separated from the surface of the photoreceptor so that the toner of the image patch is not transferred to the intermediate transfer member. Conceivable. However, in this case, after separating the intermediate transfer member from the photoreceptor between sheets, it is necessary to bring the intermediate transfer member into contact with the photoreceptor again, and a certain time difference is provided between the sheets. There is a need. Therefore, there arises a problem that the paper transport interval is widened and the throughput is lowered.

In order to suppress a decrease in throughput, it is desirable to keep the intermediate transfer member in continuous contact with the surface of the photoreceptor even between sheets of paper. In this case, as a method for maintaining the cleaner blade in good condition, for example, increasing the amount of toner when forming an image patch between sheets of paper can be considered. However, when the toner amount of the image patch is increased, the toner amount primarily transferred to the intermediate transfer body also increases accordingly. The toner transferred to the intermediate transfer member between sheets is not transferred to the sheet. Therefore, the toner transferred to the intermediate transfer member adheres to the secondary transfer roller and stains the back surface of the succeeding paper. Therefore, if an attempt is made to suppress the decrease in throughput, a new problem arises in that the amount of toner that is primarily transferred to the intermediate transfer member increases, and toner stains on the back surface of the paper become conspicuous.

JP 2013-33137 A

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and maintains a cleaner for removing toner remaining on the surface of a photoreceptor in good condition without lowering throughput, and furthermore, cleans paper and the like. An object of the present invention is to provide an image forming apparatus and a toner patch forming method capable of suppressing adhesion of toner stains to the back surface of a recording material.

In order to achieve the above object, the invention according to claim 1 is an image forming apparatus for forming a toner image on the surface of a photoreceptor, transferring the toner image to a recording material and outputting the toner image, wherein the toner image on the photoreceptor is An intermediate transfer member that primarily transfers an image and secondarily transfers it onto the recording material; a cleaner that removes residual toner remaining on the surface of the photoreceptor; and a plurality of toner images are continuously formed on the surface of the photoreceptor. forming a plurality of toner patches having the same toner density between at least two adjacent toner images at the beginning , and when the plurality of toner patches are primarily transferred from the photoreceptor to the intermediate transfer member. patch forming means for switching the primary transfer rate ; density detecting means for detecting the densities of the plurality of toner patches primarily transferred from the photoreceptor to the intermediate transfer body; is the lower limit value set so that the density of the toner patch is a toner amount that does not lower the cleaning performance of the cleaner, and the upper limit value is set so that the toner stain does not stand out on the back surface of the recording material. patch adjusting means for adjusting the amount of toner when forming the next toner patch so as to be within the range.

According to a second aspect of the invention, there is provided the image forming apparatus according to the first aspect, wherein the patch adjusting means controls the amount of exposure when the patch forming means exposes the photoreceptor so that the next and subsequent toner This configuration is characterized by adjusting the toner density of the patch.

( 3 ) In the image forming apparatus according to (1) or (2) , the patch adjusting means controls the charging potential when the patch forming means charges the photoreceptor, thereby controlling the charging potential of the photoreceptor from the next time onward. The configuration is characterized in that the toner density of each toner patch is adjusted.

The invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3 , wherein the patch adjusting means is adapted to apply toner to the surface of the photoreceptor for development by the patch forming means. The configuration is characterized in that the toner density of the next and subsequent toner patches is adjusted by controlling the developing bias.

The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4 , wherein the patch adjustment means adjusts the sub-scanning direction of the toner patch from the next time on based on the detection result of the density detection means. This configuration is characterized by adjusting the width.

A sixth aspect of the present invention is the image forming apparatus according to any one of the first to fifth aspects, wherein the patch adjustment means adjusts the frequency of toner patch formation from the next time onward based on the detection result of the density detection means. It is a configuration characterized by

A seventh aspect of the present invention is the image forming apparatus according to any one of the first to sixth aspects, wherein the patch adjustment means adjusts the size of the toner patch when forming the next and subsequent toner patches according to the size of the recording material. This configuration is characterized by adjusting the amount.

The invention according to claim 8 is the image forming apparatus according to any one of claims 1 to 7 , wherein the patch adjustment unit adjusts the frequency of forming toner patches from the next time onward in accordance with the size of the recording material. It is a configuration characterized by

The invention according to claim 9 is the image forming apparatus according to any one of claims 1 to 8 , wherein a printing rate calculation unit for calculating a printing rate in the main scanning direction of the toner image formed on the surface of the photoreceptor; and wherein the patch adjustment means adjusts the amount of toner in the main scanning direction when forming the next and subsequent toner patches according to the print rate calculated by the print rate calculation means. is.

According to a tenth aspect of the invention, there is provided an image forming apparatus that forms a toner image on a surface of a photoreceptor, primarily transfers the toner image to an intermediate transfer member, and then secondarily transfers the toner image to a recording material for output, wherein the photoreceptor is output. 1. A toner patch forming method for forming a toner patch between two adjacent toner images when a plurality of toner images are successively formed on the surface of the toner patch forming method, wherein the toner patch is formed between at least the first two adjacent toner images. a first step of forming a plurality of toner patches having the same toner concentration on the surface of the photoreceptor and switching a primary transfer rate when the plurality of toner patches are primarily transferred from the photoreceptor to the intermediate transfer member; a second step of detecting densities of the plurality of toner patches that are primarily transferred from the photoreceptor to the intermediate transfer member ; The lower limit value is set so that the cleaning performance of the cleaner that removes the residual toner remaining on the surface of the recording material does not deteriorate, and the upper limit value is set so that the toner stain is not conspicuous on the back surface of the recording material. and a third step of adjusting the amount of toner when forming toner patches from the next time so that the amount of toner is within the range of the value.

According to the present invention, a cleaner for removing toner remaining on the surface of a photoreceptor is maintained in a good state without lowering the throughput of an image forming apparatus, and toner stains adhere to the back surface of a recording material such as paper. You will be able to restrain yourself from doing it.

1 is a diagram showing a conceptual configuration of an image forming apparatus 1; FIG. 3 is a diagram showing a detailed configuration example of an image forming unit; FIG. FIG. 2 is a diagram showing an example of toner patches formed on the surface of a photoreceptor; FIG. 4 is a diagram showing an example of toner patches transferred to an intermediate transfer belt; 4 is a diagram showing the relationship between the toner density of a toner patch and the amount of exposure; FIG. 4 is a flow chart showing an example of a processing procedure performed by a controller; 5 is a flowchart showing an example of a detailed processing procedure of toner patch processing; FIG. 4 is a diagram showing another example of toner patches formed on the surface of a photoreceptor; FIG. 4 is a diagram illustrating another example of toner patches transferred to an intermediate transfer belt; 9 is a flowchart illustrating another example of detailed processing procedures of toner patch processing; FIG. 10 is a diagram showing another example of forming a toner patch; FIG. 10 is a diagram showing another example of forming a toner patch; FIG. 11 is a flowchart showing still another example of detailed processing procedures of toner patch processing; FIG. FIG. 4 is a diagram showing an example of forming three types of toner patches; FIG. 10 is a diagram showing another example of forming a toner patch;

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Elements common to each other in the embodiments described below are denoted by the same reference numerals, and redundant description thereof will be omitted.

(First embodiment)
FIG. 1 is a diagram showing a conceptual configuration of an image forming apparatus 1 that is an embodiment of the invention. An image forming apparatus 1 shown in FIG. 1 is a printer capable of forming a color image by a tandem method. This image forming apparatus 1 includes a paper feeding/conveying section 2, an image forming section 3, and a fixing section 4 inside the main body of the apparatus. It is configured to form a monochrome image and eject a recording material 9 onto a paper ejection tray 6 from an ejection port 5 at the top of the apparatus main body. The image forming apparatus 1 also includes a controller 7 inside the main body of the apparatus, and the controller 7 controls the operation of each section such as the paper feeding/conveying section 2 , the image forming section 3 and the fixing section 4 .

The paper feed transport section 2 includes a paper feed cassette 8 , a pickup roller 10 , a transport path 11 , a separation roller 12 , a leading edge detection sensor 13 , a registration roller 14 , and a secondary transfer roller 25 . .

The paper feed cassette 8 is a container that accommodates a bundle of sheet-like recording materials 9 such as printing paper. The paper feed cassette 8 can be slid, for example, in the X direction in the drawing, and can be pulled out from the bottom of the apparatus main body of the image forming apparatus 1 to be opened, or pushed into the bottom of the apparatus main body to be closed. can. For example, when the recording material 9 accommodated in the paper feed cassette 8 becomes empty, the user can replenish the recording material 9 by pulling out the paper feed cassette 8 from the bottom of the apparatus main body to open it. A wide variety of recording materials 9 can be accommodated in the paper feed cassette 8 . For example, the recording material 9 includes thin paper, thick paper, plain paper, recycled paper, coated paper, OHP film, and the like.

The transport path 11 is a path for transporting the recording material 9 in the direction of arrow F2 when the image forming apparatus 1 performs image formation on the recording material 9 . A toner image is transferred to the surface of the recording material 9 by being conveyed in the direction of arrow F2 along the conveying path 11 shown in FIG. After that, the recording material 9 is subjected to fixing processing in the fixing section 4 and discharged from the discharge port 5 . Although the conveying path 11 shown in FIG. 1 shows a conveying path for forming an image only on the surface of the recording material 9, it is not limited to this, and the recording material for forming an image on the back surface of the recording material 9 is also used. A configuration that further includes an inversion path may be used.

The pickup roller 10 picks up the recording material 9 from the upper portion of the bundle of recording materials 9 contained in the paper feed cassette 8 and conveys it to the conveying path 11 . The pickup roller 10 is in contact with one sheet of the recording material 9 positioned on the uppermost surface of the bundle of the recording materials 9, and feeds the one sheet of the recording material 9 downstream. At this time, the second sheet of recording material 9 following the recording material 9 on the uppermost surface may be carried downstream together with the recording material 9 on the uppermost surface. The separating roller 12 suppresses the second and subsequent sheets of the recording material 9 that are transported together with the recording material 9 on the uppermost surface from being led to the downstream conveying path 11, and moves only the recording material 9 on the uppermost surface to the downstream side. A roller for guidance. Therefore, the recording material 9 is conveyed one by one along the conveying path 11 on the downstream side of the separating roller 12 .

The leading edge detection sensor 13 is a sensor that detects the leading edge of the recording material 9 conveyed on the conveying path 11 . The registration roller 14 is a roller that holds the leading edge of the recording material 9 detected by the leading edge detection sensor 13 and feeds the recording material 9 to the secondary transfer roller 25 in synchronization with the image forming operation in the image forming section 3 . When the recording material 9 fed by the registration roller 14 passes the position of the secondary transfer roller 25 , the toner image primarily transferred to the intermediate transfer belt 24 is secondarily transferred to the surface of the recording material 9 . Then, the paper feeding/conveying section 2 guides the recording material 9 onto which the toner image has been transferred to the fixing section 4 .

The image forming unit 3 forms a four-color toner image of Y (yellow), M (magenta), C (cyan), and K (black) on the recording material 9 passing through the position of the secondary transfer roller 25 . It is possible to transfer toner images of these four colors at the same time. The image forming section 3 includes an exposure unit 20, image forming units 21 (21Y, 21M, 21C, 21K) provided for each color toner, and primary transfer rollers 22 (22Y , 22M, 22C, 22K), an intermediate transfer belt 24 as an intermediate transfer member, and toner bottles 23 (23Y, 23M, 23C, 23K) of respective colors.

For example, the four image forming units 21Y, 21M, 21C, and 21K are provided below the intermediate transfer belt 24, and the exposure unit 20 is further below these four image forming units 21Y, 21M, 21C, and 21K. placed in position. The toner bottles 23Y, 23M, 23C and 23K supply toner of each color to each of the four image forming units 21Y, 21M, 21C and 21K.

The exposure unit 20 exposes a photosensitive member (image carrier) provided in each of the image forming units 21Y, 21M, 21C, and 21K to expose the surface of the photosensitive member of each of the image forming units 21Y, 21M, 21C, and 21K. form a latent image. Each of the image forming units 21Y, 21M, 21C, and 21K forms a toner image on the surface of the photoreceptor by developing the electrostatic latent image with toner. The image forming units 21Y, 21M, 21C, and 21K perform primary transfer while sequentially superimposing the toner images of the respective colors onto the intermediate transfer belt 24 that circulates in the direction of the arrow F1. Therefore, when the intermediate transfer belt 24 passes the position of the most downstream image forming unit 21K, a color image is formed on the surface of the intermediate transfer belt 24 by superimposing four color toner images. However, in the case of a monochrome image, a monochrome image of only K (black) is formed on the surface of the intermediate transfer belt 24 . The toner image formed on the intermediate transfer belt 24 comes into contact with the recording material 9 conveyed by the paper feeding/conveying unit 2 when passing a position facing the secondary transfer roller 25 , and is doubled on the surface of the recording material 9 . Next transcribed.

The fixing unit 4 includes a heating roller 4a and a pressure roller 4b, and heats the recording material 9 by passing the recording material 9 onto which the toner image has been transferred between the heating roller 4a and the pressure roller 4b. The toner image is fixed on the recording material 9 by performing processing and pressure processing. The heating roller 4a is provided with a heater 4c, and the heating roller 4a is heated by the heating of the heater 4c. The recording material 9 on which the toner image is fixed in the fixing section 4 is then discharged from the discharge port 5 onto the discharge tray 6 .

A density detection sensor 28 for detecting the density of the toner image transferred to the intermediate transfer belt 24 is provided between the most downstream image forming unit 21 K and the secondary transfer roller 25 . The density detection sensor 28 is configured to detect the density of the toner image at one or more positions in the width direction of the intermediate transfer belt 24 that circulates in the arrow F1 direction. When the density detection sensor 28 detects the density of the toner image, it outputs the density value to the controller 7 . Therefore, when continuously forming toner images, the controller 7 can finely adjust the toner density based on the density detected by the density detection sensor 28 .

FIG. 2 is a diagram showing a detailed configuration example of the image forming unit 21. As shown in FIG. Although only one image forming unit 21 is illustrated in FIG. 2, the image forming units 21Y, 21M, 21C, and 21K for each color have the same configuration as in FIG. The image forming unit 21 has a cylindrical photoreceptor 30 , and is provided with a charging roller 31 , a developing section 32 , and a cleaner 34 around the photoreceptor 30 .

The photoreceptor 30 has a length substantially equal to the widthwise dimension of the intermediate transfer belt 24, and rotates in the direction of arrow R in the drawing. The charging roller 31 is a roller that charges the surface of the photosensitive member 30 rotating in the R direction to a predetermined potential. The exposure unit 20 forms an electrostatic latent image on the surface of the photoreceptor 30 by irradiating the surface of the photoreceptor 30 charged to a predetermined potential with LED light or laser light according to image data. The developing section 32 develops the electrostatic latent image formed on the photoreceptor 30 . The developing section 32 has a developing roller 33 to which a developing bias voltage is applied, and supplies the developing roller 33 with developer composed of carrier and toner while stirring. The developing roller 33 develops the electrostatic latent image with toner by applying developer to the potential gap between the potential of the electrostatic latent image and the developing bias voltage. Thereby, a toner image corresponding to the image data is formed on the surface of the photoreceptor 30 . The toner image formed on the surface of the photoreceptor 30 moves toward the position facing the primary transfer roller 22 as the photoreceptor 30 rotates in the R direction.

The primary transfer roller 22 is a roller that transfers the toner image on the photoreceptor 30 to the intermediate transfer belt 24 by applying a primary transfer bias voltage while pressing the intermediate transfer belt 24 against the photoreceptor 30 . . The primary transfer roller 22 can advance and retreat in the Z direction, and can bring the intermediate transfer belt 24 into contact with the photoreceptor 30 and separate it from the photoreceptor 30 . Also, the primary transfer roller 22 can adjust the pressing force in the Z direction when the intermediate transfer belt 24 is brought into contact with the photosensitive member 30 .

The cleaner 34 is for removing residual toner remaining on the surface of the photoreceptor 30, and is configured as a cleaner blade made of an elastic material such as rubber. The cleaner 34 is provided with the tip of the blade in contact with the surface of the photoreceptor 30, and removes residual toner from the surface of the photoreceptor 30 rotating in the R direction.

On the other hand, the controller 7 controls the operation of each unit described above. The controller 7 is connected to a network such as a LAN (Local Area Network) (not shown), and when receiving a print job via the network, drives the paper feeding/conveying unit 2, the image forming unit 3, and the fixing unit 4. , to perform image formation on the recording material 9 . The controller 7 includes a CPU and a memory (not shown). The controller 7 functions as a job control section 40, a patch forming section 41, and a patch adjusting section 42 by the CPU executing a predetermined program. The program executed by the CPU is stored in advance in a computer-readable recording medium such as a memory.

The job control section 40 controls the execution of print jobs. That is, when receiving a print job, the job control section 40 drives the paper feeding/conveying section 2, the image forming section 3, and the fixing section 4, respectively, and starts printout according to the print job. At this time, the job control unit 40 drives the photoreceptor 30, the charging roller 31, the exposure unit 20, the developing unit 32, the intermediate transfer belt 24, and the primary transfer roller 22, and drives the photoreceptor based on the image data included in the print job. An electrostatic latent image and a toner image are formed at 30 and the toner image is transferred to intermediate transfer belt 24 . When the image data included in the print job is a color image, the job control section 40 operates the four image forming units 21Y, 21M, 21C, and 21K to form a color image on the intermediate transfer belt by superimposing toner images of respective colors. 24. Further, when the image data included in the print job is a monochrome image, the job control section 40 operates only the image forming unit 21K to transfer the monochrome image consisting of only the K-color toner image onto the intermediate transfer belt 24 .

After that, the job control unit 40 conveys the recording material 9 to the position of the secondary transfer roller 25 in synchronization with the timing when the toner image transferred to the intermediate transfer belt 24 reaches the position of the secondary transfer roller 25, and performs the secondary transfer. The toner image is secondarily transferred to the recording material 9 by applying a predetermined secondary transfer bias voltage to the roller 25 . Then, the job control unit 40 drives the fixing unit 4 to fix the toner image onto the recording material 9 by performing a fixing process on the recording material 9 onto which the toner image has been transferred. 6 Drain upwards.

For example, if the print job is a job of continuously conveying a plurality of recording materials 9 to form an image, the job control unit 40 drives the primary transfer roller 22 when the first sheet of the recording material 9 starts to be conveyed. The transfer belt 24 is brought into contact with the photoreceptor 30, and the contact state between the intermediate transfer belt 24 and the photoreceptor 30 is maintained until image formation on the final recording material 9 is completed. That is, the job control unit 40 keeps the intermediate transfer belt 24 in contact with the surface of the photoreceptor 30 from the start of execution of the print job to the end of the print job. As a result, it is possible to shorten the interval at which a plurality of recording materials 9 are conveyed, thereby suppressing a decrease in throughput during execution of a print job.

When images are continuously formed on a plurality of recording materials 9, if the frictional force between the cleaner 34 and the photoreceptor 30 exceeds a certain range, the cleaner blade may be chipped or stuck, resulting in poor cleaning performance. descend. In order to prevent this, the controller 7 causes the patch forming section 41 and the patch adjusting section 42 to function to transfer images onto the recording materials 9 when the print job is a job of forming images on a plurality of recording materials 9 . A toner patch is formed between the toner images for printing. That is, the controller 7 forms a toner patch in the gap between one toner image and the next toner image sequentially formed on the surface of the photoreceptor 30 based on the image data included in the print job. of. A toner patch is not a toner image formed on photoreceptor 30 for the purpose of being transferred to recording material 9 . That is, the toner patch is a patch for supplying toner to the cleaner 34 beyond the primary transfer position by the primary transfer roller 22 in order to reduce the frictional force between the cleaner 34 and the photoreceptor 30 .

As described above, the patch forming unit 41 and the patch adjusting unit 42 function in the case of a print job in which a plurality of recording materials 9 are continuously conveyed to form an image, and the difference between the previous recording material 9 and the next recording material 9 is determined. Toner patches are formed on the surface of the photoreceptor 30 between the sheets of paper. The patch forming section 41 drives the exposure unit 20 and the image forming unit 21, and performs control for forming a toner patch between two toner images adjacent to each other. For example, the patch forming section 41 controls the exposure unit 20 between the toner image transferred onto the previous recording material 9 and the toner image transferred onto the next recording material 9 so that the toner patch is statically formed on the photoreceptor 30 . A toner patch is formed on the surface of photoreceptor 30 by forming an electrostatic latent image and developing the electrostatic latent image at developing station 32 .

FIG. 3 is a diagram showing an example of a toner patch 52 formed on the surface of photoreceptor 30. As shown in FIG. As shown in FIG. 3A, when the job control unit 40 starts executing a print job, a toner image 51 corresponding to image data included in the print job is sequentially formed on the surface of the photoreceptor 30 . . At this time, the dimension of the toner image 51 in the main scanning direction X corresponds to the size of the recording material 9, for example.

On the other hand, the patch forming section 41 forms a toner patch 52 between two toner images 51, 51 adjacent to each other. For example, FIG. 3A shows a case where a toner patch 52 is formed every time a gap between two adjacent toner images 51, 51 appears. A dimension W of the toner patch 52 in the main scanning direction X is a dimension corresponding to the entire area where a toner image can be formed on the surface of the photoreceptor 30 . That is, the toner patch is formed over the entire area in the main scanning direction X because it is necessary to supply the toner patch over the entire area where the cleaner 34 and the photoreceptor 30 are in contact with each other.

It is preferable to prevent the toner patch 52 formed on the surface of the photoreceptor 30 from being primarily transferred to the intermediate transfer belt 24 as much as possible. Therefore, as shown in FIG. 3B, the patch forming section 41 changes the primary transfer voltage applied to the primary transfer roller 22 when the portion where the toner patch 52 is formed reaches the position facing the primary transfer roller 22 . The transfer bias voltage V1 is turned off. At this time, instead of turning off the primary transfer bias voltage V1, the patch forming section 41 may apply a voltage opposite in polarity to the primary transfer bias voltage V1 to the primary transfer roller 22 . Thereby, the transfer of the toner patch 52 onto the intermediate transfer belt 24 can be suppressed. At this time, the patch forming section 41 functions as transfer control means for suppressing the transfer of the toner patch 52 onto the intermediate transfer belt 24 .

However, in this embodiment, since the primary transfer efficiency from the photoreceptor 30 to the intermediate transfer belt 24 is high, when the primary transfer bias voltage V1 is turned off, or a voltage having a polarity opposite to that of the primary transfer bias voltage V1 is applied. Even then, at least a portion of the toner patch will be transferred to intermediate transfer belt 24 .

In order to maintain the cleaning performance of the cleaner 34 by suppressing the frictional force between the cleaner 34 and the photoreceptor 30 , it is necessary to supply a predetermined amount or more of toner to the cleaner 34 using the toner patch 52 . Therefore, the toner amount of the toner patch 52 remaining on the surface of the photoreceptor 30 after passing the position of the primary transfer roller 22 needs to be equal to or greater than a predetermined lower limit value.

On the other hand, if the amount of toner used to form the toner patch 52 is increased, the amount of toner that is primarily transferred to the intermediate transfer belt 24 also increases. When the toner amount of the toner patch 52 transferred to the intermediate transfer belt 24 increases, the toner may appear as conspicuous toner contamination when adhering to the back surface of the recording material 9 that follows. In order to make this toner smudge inconspicuous, it is necessary to suppress the toner amount of the toner patch 52 transferred to the intermediate transfer belt 24 to less than a predetermined amount.

Therefore, the patch adjustment section 42 detects the density of the toner patch 52 transferred to the intermediate transfer belt 24 using the density detection sensor 28, and the patch forming section 41 forms the toner patch 52 based on the detection result. adjust the amount of toner in the

FIG. 4 is a diagram showing an example of a toner patch 52 transferred onto the intermediate transfer belt 24. As shown in FIG. As shown in FIG. 4A, a density detection sensor 28 is arranged downstream of the intermediate transfer belt 24 . FIG. 4A shows an example in which four density detection sensors 28a, 28b, 28c, and 28d are arranged at approximately equal intervals along the width direction of the intermediate transfer belt 24. FIG. These four density detection sensors 28 a , 28 b , 28 c and 28 d all measure the toner density of the toner image 51 and toner patch 52 and output the measured values to the controller 7 .

FIG. 4B shows an example of toner patch formation when a color image is formed. When a color image is formed by executing a print job, all four image forming units 21Y, 21M, 21C and 21K are used. Therefore, since the photoreceptor 30 is used in each of the image forming units 21Y, 21M, 21C and 21K, the toner patches 52 are formed in each of the image forming units 21Y, 21M, 21C and 21K. At this time, by shifting the position of the toner patch 52 formed by each of the image forming units 21Y, 21M, 21C, and 21K in the sub-scanning direction (arrow F1 direction), as shown in FIG. Toner patches 52Y, 52M, 52C and 52K of respective colors of Y, M, C and K may be separately formed between the two toner images 51 and 51, respectively. Forming the toner patches 52Y, 52M, 52C and 52K of each color individually has the advantage that the density detection sensors 28a, 28b, 28c and 28d can individually measure the toner density of each color.

The patch adjusting section 42 adjusts the toner amount of the toner patch 52 formed by the patch forming section 41 based on the density of the toner patch 52 on the intermediate transfer belt 24 measured as described above. As a result, the patch forming unit 41 sets the toner amount when forming the toner patch 52 on the surface of the photoreceptor 30 to a toner amount that does not make the toner stains noticeable on the back surface of the recording material 9 that follows. It is possible to set the amount of toner to such an extent that the cleaning performance by cleaning is not degraded. As a result, the cleaner 34 for removing the toner remaining on the surface of the photoreceptor 30 can be kept in a good state without lowering the throughput at the time of printing output, and the adhesion of toner stains to the back surface of the recording material 9 can be prevented. It can be suppressed.

For example, when the execution of a print job is started and the patch forming unit 41 forms the first toner patch 52 on the surface of the photoreceptor 30, the patch forming unit 41 sets the toner amount corresponding to a predetermined default value or the previous print job amount. A toner patch 52 is formed by setting the toner amount determined during the execution of . When the first toner patch 52 is primarily transferred onto the intermediate transfer belt 24 , the patch adjustment unit 42 acquires the density value of the toner patch 52 detected by the density detection sensor 28 and transfers the toner patch on the intermediate transfer belt 24 to the toner patch 52 . Based on the density value of 52, the density value of the toner patch 52 to be formed next time and thereafter is determined. The patch forming section 41 forms the toner patches 52 based on the density values determined by the patch adjusting section 42 when forming the toner patches 52 from the next time onward.

There are several methods for adjusting the amount of toner when the patch forming section 41 forms the toner patch 52 . For example, if the exposure amount of the photoreceptor 30 by the exposure unit 20 is changed, the toner density of the toner patch 52 is changed accordingly, so the amount of toner used for the toner patch 52 can be changed. Further, for example, by changing the potential when the charging roller 31 charges the photosensitive member 30, the toner density can be changed accordingly. Also, the toner concentration can be changed by changing the developing bias voltage applied to the developing roller 33, for example. Furthermore, the amount of toner can also be changed by changing the width of the toner patch 52 in the sub-scanning direction (corresponding to the exposure time). The patch forming section 41 adjusts the toner amount of the toner patch 52 by combining these multiple methods. Note that the patch forming section 41 may adjust the toner amount by adopting only one method among the plurality of methods described above.

On the other hand, the patch adjustment unit 42 determines the primary transfer rate (from the photoreceptor 30 to the intermediate transfer belt 24 ) can be stored in advance. Therefore, the patch adjustment unit 42 calculates the toner density of the toner patch 52 remaining on the surface of the photoreceptor 30 after passing the primary transfer position from the density value of the toner patch 52 detected by the density detection sensor 28 . be able to. Therefore, the patch adjusting section 42 determines that the toner density of the toner patch 52 remaining on the surface of the photoreceptor 30 is equal to or higher than the predetermined lower limit, and that the toner density of the toner patch 52 detected by the density detection sensor 28 is a predetermined value. It is possible to determine the amount of exposure that is less than the upper limit of .

FIG. 5 is a diagram showing the relationship between the toner density of the toner patch 52 and the amount of exposure. A solid line L1 in FIG. 5 indicates the toner density of the toner patch 52 transferred to the intermediate transfer belt 24 and detected by the density detection sensor 28 . A dashed line L2 indicates the toner density at the time when the patch forming unit 41 forms the toner patch 52 on the surface of the photoreceptor 30 . After obtaining the density value D1 of the toner patch 52 measured by the density detection sensor 28 , the patch adjustment unit 42 performs calculation based on the primary transfer rate based on the density value D1, A density value D2 is calculated when the toner patch 52 is formed on the surface. That is, the density value D2 is the density value of the toner patch 52 before being primarily transferred to the intermediate transfer belt 24 . The patch adjustment unit 42 calculates a difference D3 between the density value D2 of the toner patch 52 formed on the photoreceptor 30 and the density value D1 of the toner patch 52 primarily transferred to the intermediate transfer belt 24 . This difference D3 corresponds to the density value of residual toner remaining on the surface of the photoreceptor 30 after the primary transfer. Therefore, the patch adjustment unit 42 can determine the exposure amount at which the density value D3 is equal to or greater than the predetermined lower limit value and the density value D1 is less than the predetermined upper limit value.

However, the patch adjustment unit 42 does not necessarily have to perform the calculation described above. That is, as shown in FIG. 5, the relationship between the toner density and the exposure amount can be linearly approximated. Also, the solid line L1 and the dashed line L2 are correlated and differ only in their slopes. Therefore, a lower limit value Dmin and an upper limit value Dmax are set for the density value D1 detected by the density detection sensor 28, and exposure is performed so that the density value D1 is within the range between the lower limit value Dmin and the upper limit value Dmax. You may make it determine the quantity. In this case, the lower limit value Dmin is a lower limit value set so that the amount of toner supplied to the cleaner 34 does not deteriorate the cleaning performance. The upper limit value Dmax is an upper limit value that is set so that toner stains on the back surface of the recording material 9 are not conspicuous. Therefore, if the density value D1 detected by the density detection sensor 28 is less than the lower limit value Dmin, the patch adjustment section 42 instructs the patch formation section 41 to increase the exposure amount of the exposure unit 20, and the density value If D1 is equal to or greater than the upper limit value Dmax, it is possible to instruct the patch forming section 41 to decrease the exposure amount of the exposure unit 20 . As a result, when the next toner patch 52 is formed on the surface of the photoreceptor 30 , the patch forming unit 41 can expose the photoreceptor 30 based on the exposure amount instructed by the patch adjustment unit 42 . As a result, the toner patch 52 formed on the photoreceptor 30 has a toner amount that does not lower the cleaning performance of the cleaner 34, and moreover, the toner stain on the back surface of the recording material 9 caused by the toner primarily transferred to the intermediate transfer belt 24 is conspicuous. The amount of toner becomes to the extent that it does not exist.

Next, an example of operations in the image forming apparatus 1 will be described. FIG. 6 is a flow chart showing an example of a processing procedure performed by the controller 7. As shown in FIG. The processing based on this flowchart is performed by the CPU of the controller 7 executing a predetermined program. When the controller 7 starts this process, it waits until it receives a print job (step S1), and when it receives the print job (YES in step S1), it starts executing the received print job (step S2). As a result, the image forming apparatus 1 starts feeding and conveying the recording material 9, and the intermediate transfer belt 24 comes into contact with the photoreceptor 30, thereby starting an operation for transferring the toner image onto the recording material 9. be done.

When execution of the print job is started, the controller 7 determines whether it is time to form the toner patch 52 (step S3). For example, if the print job is a job of forming images on a plurality of recording materials 9, the controller 7 may set the toner patch 52 at the timing when the exposure process for forming the toner image corresponding to the print job is completed. If it is the timing to form, it is determined as YES in step S3. When the controller 7 determines that it is time to form the toner patch 52 during execution of the print job (YES in step S3), the controller 7 executes toner patch processing (step S4). On the other hand, if it is determined that it is not the time to form the toner patch 52 (NO in step S3), the process of step S4 is skipped. After that, the controller 7 determines whether or not the execution of the print job is finished (step S5). repeat. Therefore, the toner patch process (step S4) is repeatedly performed each time it is determined that it is time to form the toner patch 52 during execution of the print job. When the execution of the print job ends (YES in step S5), the processing by the controller 7 ends.

FIG. 7 is a flowchart showing an example of a detailed processing procedure of toner patch processing (step S4). When starting the toner patch processing (step S4), the controller 7 first sets exposure conditions for forming the toner patch 52 (step S10). The exposure conditions set here include, for example, exposure amount, exposure time, and exposure frequency. The exposure frequency is the frequency at which the toner patches 52 are formed, and the value of N is determined when the toner patches 52 are formed once each time N toner images are formed (where N is an integer equal to or greater than 1). It is. For example, when forming the first toner patch 52 after the start of execution of the print job, the controller 7 sets the exposure amount, the exposure time, and the exposure frequency corresponding to predetermined default values as the exposure conditions. However, the present invention is not limited to this, and the exposure conditions determined during execution of the previous print job may be set. Also, if the exposure conditions have already been determined during execution of the current print job, the controller 7 sets the exposure conditions that have already been determined.

After setting the exposure conditions, the controller 7 forms the toner patches 52 based on the exposure conditions (step S11). That is, an electrostatic latent image of the toner patch 52 is formed by exposing the photoreceptor 30 under the exposure conditions set in step S10, and the toner is formed on the surface of the photoreceptor 30 by developing the electrostatic latent image. A patch 52 is formed. After forming the toner patch 52 on the surface of the photoreceptor 30, the controller 7 turns off the primary transfer bias voltage V1 immediately before the toner patch 52 reaches the primary transfer position (step S12). As a result, transfer of toner from the photoreceptor 30 to the intermediate transfer belt 24 can be suppressed. However, at least a portion of toner patch 52 will be transferred to intermediate transfer belt 24 .

After that, the controller 7 acquires the density value D1 of the toner patch 52 detected by the density detection sensor 28 (step S13), and determines whether or not the density value D1 is equal to or greater than a predetermined lower limit value Dmin (step S14). If the density value D1 is less than the lower limit value Dmin (NO in step S14), the controller 7 increases the exposure amount when forming the next toner patch 52 (step S15). As a result, the next toner patch 52 is formed with a toner amount that does not degrade the cleaning performance of the cleaner 34 .

On the other hand, if the density value D1 is equal to or greater than the predetermined lower limit value Dmin (YES in step S14), the controller 7 determines whether the density value D1 is less than the predetermined upper limit value Dmax (step S16). If the density value D1 is equal to or greater than the upper limit value Dmax (NO in step S16), the controller 7 reduces the exposure amount when forming the next toner patch 52 (step S17). As a result, the next toner patch 52 is formed with a toner amount that does not cause toner stains on the back surface of the recording material 9 .

Subsequently, the controller 7 determines whether or not other exposure conditions need to be changed (step S18). Here, it is determined whether or not it is necessary to change the exposure time and exposure frequency for forming the toner patch 52 . If other exposure conditions need to be changed (YES in step S18), the controller 7 changes the exposure time for forming the next toner patch 52 (step S19). As a result, the width (dimension) of the toner patch 52 in the sub-scanning direction is changed, and the amount of toner used for the toner patch 52 can be adjusted. The controller 7 also changes the exposure frequency for forming the toner patches 52 (step S20). This makes it possible to adjust the frequency with which toner patches 52 are formed during execution of a print job. If it is not necessary to change other exposure conditions (NO in step S18), the toner patch process (step S4) ends.

As described above, in the image forming apparatus 1 of the present embodiment, in order to prevent the cleaning performance of the cleaner 34 from deteriorating, when a print job for continuously forming images on a plurality of recording materials 9 is executed, A toner patch 52 is formed between two toner images 51 , 51 that are sequentially formed based on a print job, and the toner used for the toner patch 52 is supplied to the cleaner 34 . Since the image forming apparatus 1 keeps the intermediate transfer belt 24 in contact with the photoreceptor 30 even when the toner patch 52 is formed on the photoreceptor 30, the throughput during print output is not reduced. . Further, when the image forming apparatus 1 forms the toner patches 52 on the photoreceptor 30 during execution of the print job, the image forming apparatus 1 detects the toner density of the toner patches 52 that are primarily transferred from the photoreceptor 30 to the intermediate transfer belt 24, and detects the toner density. Based on the result, the amount of toner for forming the toner patch 52 from the next time onward is adjusted. Such an image forming apparatus 1 directly measures the toner density of the toner patch 52 transferred to the intermediate transfer belt 24 and adjusts the toner amount of the toner patch 52 from the next time onward. It is possible to maintain the optimum amount of toner supplied to the cleaner 34 while suppressing the adhesion of toner stains.

By the way, the exposure condition for forming the first toner patch 52 after the start of execution of the print job may be set according to the size of the recording material 9 . That is, when the size of the recording material 9 changes, the size of the toner image 51 formed on the surface of the photoreceptor 30 also changes. Accordingly, the size of the toner image 51 in the sub-scanning direction also changes. will vary depending on the size of The toner image 51 based on the print job is transferred from the photosensitive member 30 to the intermediate transfer belt 24 at a primary transfer rate of nearly 100%. will continue for a long time. Therefore, as the size of the recording material 9 increases, the amount of toner to be supplied to the cleaner 34 between the two toner images 51, 51 increases. Conversely, when the size of the recording material 9 is small, the amount of toner to be supplied to the cleaner 34 between the two toner images 51, 51 is small. For this reason, the exposure conditions for forming the toner patch 52 may be adjusted according to the size of the recording material 9, and the toner amount of the toner patch 52 may be determined according to the size of the recording material 9. do not have. An example is shown in Table 1 below.

For example, focusing on the recording material 9 of "A4L" in Table 1, the length of the recording material 9 in the sub-scanning direction is 210 mm, and the required amount of toner for the toner patch 52 to be formed between the two toner images 51, 51 is 1 mg/sheet. On the other hand, if the exposure conditions for forming the toner patch 52 are set to certain conditions, the amount of toner that can be supplied to the cleaner 34 with one toner patch 52 is 1.00 mg/time. This toner amount is constant regardless of the size of the recording material 9 .

Next, focusing on the "A6S" recording material 9, the length of the recording material 9 in the sub-scanning direction is 105 mm, and the required amount of toner for the toner patch 52 to be formed between the two toner images 51 is 0.5 mm. 50 mg/sheet. That is, when the recording material 9 of "A4L" is compared with the recording material 9 of "A6S" as a reference, the length of the recording material 9 of "A6S" in the sub-scanning direction is 1/2. Occurs twice as often. Therefore, the required amount of toner for the toner patch 52 to be formed in the gap is 0.5 mg/sheet, which is half that of the recording material 9 of "A4L". Therefore, when the recording material 9 is "A6S", the patch adjustment unit 42 may reduce the exposure amount for "A4L" to 1/2, or set the exposure time to 1/2 to The width of the patch 52 in the sub-scanning direction may be halved. Further, the patch adjustment unit 42 forms the toner patch 52 once every time a gap appears two times instead of forming the toner patch 52 every time a gap between the toner images 51 appears. You can do it.

Next, focusing on the recording material 9 of "A3S", the length of the recording material 9 in the sub-scanning direction is 420 mm, and the required amount of toner for the toner patch 52 to be formed between the two toner images 51 is 2.5 mm. 00 mg/sheet. That is, when the recording material 9 of "A4L" is compared with the recording material 9 of "A3S" as a reference, the length of the recording material 9 of "A3S" in the sub-scanning direction is doubled. becomes 1/2. Therefore, the required amount of toner for the toner patch 52 to be formed in the gap is 2.0 mg/sheet, which is twice that of the recording material 9 of "A4L". Therefore, when the recording material 9 is "A3S", the patch adjustment unit 42 may double the exposure amount for "A4L", or double the exposure time to may be doubled in the sub-scanning direction.

In this manner, the patch adjustment unit 42 adjusts the amount of toner when forming the toner patch 52 according to the size of the recording material 9 , so that regardless of the size of the recording material 9 used, the amount of toner can be adjusted. It becomes possible to supply enough toner to the cleaner 34 during execution of the print job so as not to degrade the cleaning performance. Even in this case, during execution of the print job, the toner amount of the toner patch 52 to be formed from the next time onward is determined based on the density value of the toner patch 52 detected by the density detection sensor 28, as described above. Of course it will be adjusted.

(Second embodiment)
Next, a second embodiment of the invention will be described. In this embodiment, an example in which a plurality of toner patches 52 are formed between two toner images 51 adjacent to each other will be described. Also in this embodiment, the configuration of the image forming apparatus 1 is the same as that described in the first embodiment.

FIG. 8 is a diagram showing an example of the toner patch 52 formed on the surface of the photoreceptor 30 in this embodiment. As shown in FIG. 8, when job control unit 40 starts executing a print job, toner images 51 corresponding to image data included in the print job are sequentially formed on the surface of photoreceptor 30 .

On the other hand, the patch forming section 41 forms two toner patches 52, 52 between the two toner images 51, 51 adjacent to each other. For example, FIG. 8 shows a case where two toner patches 52, 52 are formed each time a gap between two adjacent toner images 51, 51 appears. Also, the toner densities of the two toner patches 52, 52 are the same.

When the two toner patches 52, 52 pass the primary transfer position, the patch forming section 41 transfers one toner patch 52 to the intermediate transfer belt 24 in the same manner as the toner image 51, and transfers the other toner patch 52. suppress That is, the patch forming section 41 reduces the primary transfer bias voltage V1 applied to the primary transfer roller 22 when the first toner patch 52 formed following the previous toner image 51 passes the primary transfer position. The on state is maintained, and when the second toner patch 52 passes the primary transfer position, the primary transfer bias voltage V1 applied to the primary transfer roller 22 is turned off. Instead of turning off the primary transfer bias voltage V1, a voltage having a polarity opposite to that of the primary transfer bias voltage V1 may be applied. As a result, the first toner patch 52 is transferred to the intermediate transfer belt 24 at a primary transfer rate close to 100%. Further, since the transfer of the second toner patch 52 to the intermediate transfer belt 24 is suppressed, the amount of toner transferred to the intermediate transfer belt 24 is reduced.

FIG. 9 is a diagram showing an example of toner patches 52 transferred to the intermediate transfer belt 24 in this embodiment. By changing the primary transfer bias voltage V1 when each of the two toner patches 52, 52 passes through the primary transfer position as described above, the intermediate transfer belt 24 is provided with the toner patch 52a having a high toner density and the , and a toner patch 52b having a low toner density are formed. The toner densities of these two types of toner patches 52a and 52b are detected when they pass the position where the density detection sensor 28 is provided. That is, the toner density detected from the dark toner patch 52a corresponds to the density value D2 of the dashed line L2 shown in FIG. Also, the toner density detected from the thin toner patch 52b corresponds to the density value D1 of the solid line L1 shown in FIG. That is, the image forming apparatus 1 of the present embodiment is different from the first embodiment in that it actually measures both the density values D1 and D2 shown in FIG. This is a different point. By actually measuring both the density values D1 and D2 in this way, it is possible to accurately calculate the density value D3 of the toner of the toner patch 52b remaining on the surface of the photoreceptor 30 after passing the primary transfer position. There is an advantage.

Next, an example of the operation of the image forming apparatus 1 of this embodiment will be described. The main processing procedure by the controller 7 is the same as the flowchart of FIG. 6 shown in the first embodiment. On the other hand, in this embodiment, the toner patch process (step S4) is different from that in the first embodiment. The toner patch processing (step S4) of this embodiment will be described below.

FIG. 10 is a flowchart showing an example of a detailed processing procedure of toner patch processing (step S4) in this embodiment. When starting the toner patch processing (step S4), the controller 7 first sets exposure conditions for forming the toner patch 52 (step S30). This process is the same as the process of step S7 shown in FIG. After setting the exposure conditions, the controller 7 forms the toner patches 52 based on the exposure conditions (step S31). At this time, the controller 7 forms two toner patches 52, 52 having the same toner density between the two toner images 51, 51. FIG. When the first toner patch 52 passes the primary transfer position, the controller 7 keeps the primary transfer bias voltage V1 on (step S32), and the second toner patch 52 passes the primary transfer position. When doing so, the primary transfer bias voltage V1 is turned off (step S33). As a result, two types of toner patches 52a and 52b having different toner densities can be formed on the intermediate transfer belt 24. FIG.

After that, the controller 7 obtains the density values D1 and D2 of the two types of toner patches 52a and 52b detected by the density detection sensor 28 (step S34), and the toner patch 52b remaining on the surface of the photoreceptor 30. A density value D3 is calculated. The controller 7 determines whether or not the density value D3 is greater than or equal to a predetermined lower limit (step S36). The amount of exposure during formation is increased (step S37). As a result, the next toner patch 52 is formed with a toner amount that does not degrade the cleaning performance of the cleaner 34 .

On the other hand, if the density value D3 is greater than or equal to the lower limit value (YES in step S36), the controller 7 then determines whether the density value D2 of the toner patch 52a is less than the predetermined upper limit value (step S38). If the density value D2 is equal to or greater than the upper limit value (NO in step S38), the amount of exposure for forming the next toner patch 52 is decreased (step S39). As a result, the next toner patch 52 is formed with a toner amount that does not cause toner stains on the back surface of the recording material 9 .

Subsequently, the controller 7 determines whether or not other exposure conditions need to be changed (step S40), and if other exposure conditions need to be changed (YES in step S40), the exposure time and exposure frequency is changed (steps S41 and S42). If it is not necessary to change other exposure conditions (NO in step S40), the toner patch process (step S4) ends.

By the way, in the above, when the toner patches 52 are formed during execution of the print job, the case where two toner patches 52 having the same toner density are formed each time is exemplified. However, the present invention is not limited to this, and when the first toner patch 52 is formed after the execution of the print job is started, two toner patches 52 having the same toner density are formed, and subsequent toner patches 52 are formed. When doing so, only one toner patch 52 adjusted to the optimum toner amount (toner density) may be formed.

FIG. 11 is a diagram illustrating a case where two toner patches 52, 52 having the same toner density are first formed, and only one toner patch 52 with an adjusted toner density is formed from the second time onward. As shown in FIG. 11, when job control unit 40 starts executing a print job, toner images 51 corresponding to image data included in the print job are sequentially formed on the surface of photoreceptor 30 . After the start of execution of the print job, the patch forming section 41 forms the first toner patch 52 between the two toner images 51, 51 adjacent to each other. Form.

When the two toner patches 52, 52 pass the primary transfer position, the patch forming section 41 transfers one toner patch 52 to the intermediate transfer belt 24 in the same manner as the toner image 51, and transfers the other toner patch 52. suppress As a result, one toner patch 52 is transferred to the intermediate transfer belt 24 at a primary transfer rate close to 100%, and the transfer of the other toner patch 52 to the intermediate transfer belt 24 is suppressed. Then, the patch adjustment unit 42 acquires the density values D1 and D2 of the two types of toner patches 52a and 52b transferred to the intermediate transfer belt 24, and the toner density when forming the toner patches 52 for the second and subsequent times is set to a predetermined upper limit. Adjust so that it is within the range of value and lower limit. Therefore, as shown in FIG. 11, the patch forming section 41 forms only one toner patch 52 whose toner density is adjusted to the optimum state when forming the second and subsequent toner patches 52 during execution of the print job. can be formed.

Note that the present embodiment is the same as that described in the first embodiment except for the points described above.

(Third embodiment)
Next, a third embodiment of the invention will be described. In the above-described second embodiment, the case where the two toner patches 52, 52 having the same toner density are formed and the toner density transferred to the intermediate transfer belt 24 is measured. In this embodiment, when forming the first toner patch 52 after starting execution of a print job, an example will be described in which two types of toner patches having different toner densities are formed.

FIG. 12 is a diagram illustrating a case where two types of toner patches 52c and 52d with different toner densities are first formed, and only one toner patch 52 with an adjusted toner density is formed after the second time. As shown in FIG. 12, when job control unit 40 starts executing a print job, toner images 51 corresponding to image data included in the print job are sequentially formed on the surface of photoreceptor 30 . After the execution of the print job is started, the patch forming section 41 forms the first toner patch 52 between the two toner images 51, 51 adjacent to each other by, for example, changing the exposure amount of the exposure unit 20. Two types of toner patches 52 c and 52 d with different densities are formed on the photosensitive member 30 .

The patch forming section 41 prevents the toner patches 52 from being transferred to the intermediate transfer belt 24 when the two types of toner patches 52c and 52d pass through the primary transfer position. In other words, both of the two types of toner patches 52c and 52d are allowed to pass through the primary transfer position under the same conditions in which the primary transfer onto the intermediate transfer belt 24 is suppressed. As a result, the two types of toner patches 52c and 52d are transferred onto the intermediate transfer belt 24 at the same primary transfer rate.

The patch adjustment unit 42 acquires the density values of the two types of toner patches 52c and 52d transferred onto the intermediate transfer belt 24. FIG. Both of the two density values acquired at this time are density values located on the solid line L1 shown in FIG. Therefore, the patch adjustment unit 42 can accurately obtain a characteristic line corresponding to the solid line L1 shown in FIG. 5 by calculating a straight line through which two density values pass. After obtaining the correct solid line L1, the patch adjustment unit 42 adjusts the toner density so that the toner density when forming the toner patch 52 from the next time onwards is within the range of the predetermined upper limit value and lower limit value. Therefore, as shown in FIG. 12, the patch forming section 41 forms only one toner patch 52 whose toner density is adjusted to the optimum state when forming the second and subsequent toner patches 52 during execution of the print job. can be formed.

The main processing procedure by the controller 7 for forming the toner patch 52 as described above is the same as the flow chart of FIG. 6 shown in the first embodiment. On the other hand, in this embodiment, the toner patch process (step S4) is different from that in the first and second embodiments. The toner patch processing (step S4) of this embodiment will be described below.

FIG. 13 is a flowchart showing an example of a detailed processing procedure of toner patch processing (step S4) in the third embodiment. When starting the toner patch process (step S4), the controller 7 first determines whether or not it is the first toner patch 52 after the start of execution of the print job (step S51). If it is the first toner patch 52 (YES in step S51), the controller 7 sets first exposure conditions for forming the first toner patch 52c (step S52), and based on the first exposure conditions to form the first toner patch 52c on the photosensitive member 30 (step S53). Next, the controller 7 sets second exposure conditions for forming the second toner patches 52d (step S54), and forms the second toner patches 52d on the photoreceptor 30 based on the second exposure conditions. (step S55). As a result, two types of toner patches 52 c and 52 d with different toner densities are formed on the surface of the photoreceptor 30 .

Then, the controller 7 turns off the primary transfer bias voltage V1 of the primary transfer roller 22 when the two types of toner patches 52c and 52d pass the primary transfer position (step S56). As a result, the two types of toner patches 52c and 52d having different toner densities are transferred onto the intermediate transfer belt 24 while the primary transfer rate onto the intermediate transfer belt 24 is suppressed.

After that, the controller 7 acquires the density values of the two types of toner patches 52c and 52d detected by the density detection sensor 28 (step S57), and calculates a characteristic line corresponding to the solid line L1 in FIG. 5 (step S58). . Based on the characteristic line, the controller 7 determines the amount of exposure such that the toner amount of the toner patch 52 is within the range of the predetermined upper limit and lower limit (step S59). As a result, the toner amount of the toner patch 52 from the next time onwards is adjusted to be within the range of the predetermined upper limit value and the lower limit value.

Subsequently, the controller 7 determines whether or not other exposure conditions need to be changed (step S60), and if other exposure conditions need to be changed (YES in step S60), the exposure time and exposure frequency is changed (steps S61 and S62). If it is not necessary to change other exposure conditions (NO in step S60), the toner patch process (step S4) ends.

If the toner patch 52 is not the first toner patch 52 after the start of execution of the print job (NO in step S51), the controller 7 sets exposure conditions that have already been determined (step S63), and based on the exposure conditions, A toner patch 52 is formed in 30 (step S64). Then, the controller 7 turns off the primary transfer bias voltage V1 of the primary transfer roller 22 when the toner patch 52 passes the primary transfer position (step S65). After that, the controller 7 acquires the density value D1 of the toner patch 52 detected by the density detection sensor 28 (step S66), and determines whether the toner amount of the toner patch 52 is within the range of the predetermined upper limit value and lower limit value. (step S67). If it is within the range of the predetermined upper and lower limits, an appropriate amount of toner is supplied to the cleaner 34, and the toner stains on the back surface of the recording material 9 are inconspicuous. No further adjustments are required. Therefore, if the amount of toner in the toner patch 52 is within the range of the predetermined upper limit and lower limit (YES in step S67), the toner patch process (step S4) ends.

On the other hand, if the toner amount of the toner patch 52 is not within the predetermined upper limit and lower limit (NO in step S67), the controller 7 readjusts the exposure amount (step S68). For this readjustment processing, for example, the processing described in the first embodiment may be adopted. If the exposure amount has been readjusted, the processing by the controller 7 proceeds to step S60. Therefore, other exposure conditions such as exposure time and exposure frequency are readjusted as necessary.

In this embodiment, two types of toner patches 52c and 52d with different toner densities are formed when forming the first toner patch 52 after the start of execution of the print job. However, the number of types of toner patches 52 is not limited to two, and may be three or more. FIG. 14 is a diagram showing an example of forming three types of toner patches 52c, 52d, and 52e. FIG. 14A shows an example in which three types of toner patches 52c, 52d, and 52e having different toner densities are formed between the toner image 51 of the first sheet and the toner image 51 of the second sheet. By forming three or more types of toner patches 52c, 52d, and 52e in this way and calculating the characteristic line corresponding to the solid line L1 in FIG. 5, there is an advantage that the reliability of the characteristic line is improved.

If it is difficult to form three or more types of toner patches 52 between two toner images 51, 51, three types of toner patches 52c, 52d, and 52e are formed as shown in FIG. You may make it form one by one. In this case, since the third toner patch 52e is formed between the third toner image 51 and the fourth toner image 51, the process of calculating the characteristic line corresponding to the solid line L1 in FIG. is performed after the third toner image 51 is formed.

Note that the present embodiment is the same as that described in the first embodiment or the second embodiment except for the points described above.

(Fourth embodiment)
Next, a fourth embodiment of the invention will be described. In this embodiment, when the toner patch 52 is formed, the amount of toner in the main scanning direction X of the toner patch 52 is adjusted according to the printing ratio in the main scanning direction X of the toner image 51 previously formed on the photoreceptor 30 . An example of

FIG. 15 is a diagram showing an example of the toner patch 52 formed in this embodiment. In this embodiment, when the patch forming unit 41 forms the toner patch 52, the printing rate (density distribution) in the main scanning direction X of the immediately preceding toner image 51 is calculated and the printing rate is analyzed. For example, as shown in FIG. 15(a), the patch forming section 41 divides the entire region in the main scanning direction X in which the toner patch 52 can be formed into a plurality of regions R1 to R8. , the printing rate (density distribution) of the toner image 51 immediately before is calculated. At this time, the patch forming section 41 functions as a printing ratio calculating means.

Then, when forming the toner patch 52, the patch forming section 41 adjusts the amount of toner to be used for the areas R1 to R8 according to the printing rate of the toner image 51 immediately before. For example, as shown in FIG. 15(b), the patch forming unit 41 sets the toner concentration to be low in areas with high coverage in the immediately preceding toner image 51 among the plurality of areas R1 to R8. A toner patch 52 is formed by setting a high toner density in a region with a low . In this case, the toner patch 52 formed on the photoreceptor 30 becomes a patch image having different toner densities in the main scanning direction X. FIG. That is, the amount of toner increases in areas where the toner density is high, and the amount of toner decreases in areas where the toner density is low.

Further, instead of adjusting the toner density according to the printing rate, as shown in FIG. ) may be changed. That is, as shown in FIG. 15C, the patch forming unit 41 sets short the exposure time for the areas with high coverage in the immediately preceding toner image 51 among the plurality of areas R1 to R8. A toner patch 52 is formed by setting a longer exposure time in a region with a lower . As a result, the toner patches 52 formed on the photoreceptor 30 form patch images having different lengths in the sub-scanning direction Y for each of the regions R1 to R8 arranged along the main scanning direction X. FIG. That is, the amount of toner increases in areas that are long in the sub-scanning direction Y, and the amount of toner decreases in areas that are short in the sub-scanning direction Y.

In this manner, the main scanning direction X is divided into a plurality of regions R1 to R8, and when the toner patch 52 is formed, the amount of toner used in each region is adjusted according to the printing ratio of the immediately preceding toner image 51. The amount of toner supplied to the cleaner 34 can be made uniform in the main scanning direction X during job execution. As a result, since the frictional force between the cleaner 34 and the photoreceptor 30 can be made uniform in the main scanning direction X, it is possible to suppress the occurrence of localized defects in the cleaner blade. Further, according to the present embodiment, the amount of toner used to form the toner patch 52 can be minimized, so the amount of toner consumed can be reduced.

In this embodiment, when the toner patch 52 is formed, the printing rate in the main scanning direction X of the immediately preceding toner image 51 is analyzed, and the toner amount in the main scanning direction X of the toner patch 52 is adjusted. exemplified. However, the toner image 51 to be analyzed by the patch forming section 41 is not limited to the toner image 51 of the immediately preceding sheet. In the case of formation, it is preferable to analyze a predetermined number of toner images 51 before the toner patches 52 are formed.

Further, when adjusting the toner amounts of the plurality of regions R1 to R8 individually as in the present embodiment, the density detection sensor 28 is separately provided for each of the regions R1 to R8, and each density detection sensor 28 is preferably configured so that it can detect the toner density of each of the regions R1 to R8.

In the above description, the patch forming unit 41 calculates the printing rate of the immediately preceding toner image 51 in the main scanning direction X, and adjusts the amount of toner used for each of the regions R1 to R8 based on the printing rate. However, the present invention is not limited to this, and similar processing may be performed in the patch adjustment section 42 . Also, the method of adjusting the toner amount in the main scanning direction X described in this embodiment can be applied to any of the first to third embodiments described above.

(Modification)
Several embodiments of the present invention have been described above. However, the present invention is not limited to the contents described in each of the above embodiments, and various modifications are applicable.

For example, in the above embodiment, the image forming apparatus 1 is configured as a printer, but the present invention is not limited to this. For example, the image forming apparatus 1 may be configured as an apparatus having multiple functions such as an MFP (Multifunction Peripherals), and the printer function may be installed as one of the multiple functions. do not have.

Further, in the above embodiment, the image forming apparatus 1 is a color machine capable of forming color images. However, the image forming apparatus 1 is not limited to this, and may be a monochrome dedicated machine capable of forming only monochrome images.

1 image forming apparatus 3 image forming section 7 controller (transfer control means)
9 recording material 21 (21Y, 21M, 21C, 21K) image forming unit 22 (22Y, 22M, 22C, 22K) primary transfer roller 24 intermediate transfer belt (intermediate transfer body)
28 (28a to 28d) concentration detection sensor (concentration detection means)
30 photoreceptor 34 cleaner 40 job control section (job control means)
41 patch forming unit (patch forming means)
42 patch adjustment section (patch adjustment means)

Claims (10)

An image forming apparatus that forms a toner image on the surface of a photoreceptor, transfers the toner image to a recording material, and outputs the toner image,
an intermediate transfer member that primarily transfers the toner image of the photoreceptor and secondarily transfers it onto the recording material;
a cleaner for removing residual toner remaining on the surface of the photoreceptor;
When a plurality of toner images are continuously formed on the surface of the photoreceptor, a plurality of toner patches having the same toner density are formed between at least two first adjacent toner images , and the plurality of toner patches are patch forming means for switching a primary transfer rate when primary transfer is performed from the photosensitive member to the intermediate transfer member ;
density detection means for detecting the density of the plurality of toner patches that are primarily transferred from the photoreceptor to the intermediate transfer body;
a lower limit value that is set based on the detection result of the density detection means so that the density of the next and subsequent toner patches will be a toner amount that does not degrade the cleaning performance of the cleaner; patch adjustment means for adjusting the amount of toner when forming subsequent toner patches so as to be within the range of the upper limit set so as not to stand out;
An image forming apparatus comprising: 2. The image according to claim 1 , wherein said patch adjusting means adjusts the toner density of subsequent toner patches by controlling the amount of exposure when said patch forming means exposes said photosensitive member. forming device. 3. The patch adjustment device according to claim 1 , wherein the patch adjustment device adjusts the toner density of subsequent toner patches by controlling the charge potential when the patch formation device charges the photosensitive member. image forming device. The patch adjusting means is characterized in that the patch forming means adjusts the toner density of subsequent toner patches by controlling a developing bias when the patch forming means applies toner to the surface of the photoreceptor for development. 4. The image forming apparatus according to claim 1 . 5. The image forming apparatus according to claim 1, wherein said patch adjusting means adjusts the width of the toner patch in the sub-scanning direction from the next time on based on the detection result of said density detecting means. 6. The image forming apparatus according to claim 1, wherein said patch adjusting means adjusts the frequency of forming toner patches from the next time on based on the detection result of said density detecting means. 7. The image forming apparatus according to claim 1, wherein said patch adjustment means adjusts the amount of toner when forming toner patches from the next time onward according to the size of said recording material. 8. The image forming apparatus according to claim 1, wherein said patch adjustment means adjusts the frequency of forming toner patches from the next time onward according to the size of said recording material. printing ratio calculating means for calculating a printing ratio in the main scanning direction of the toner image formed on the surface of the photoreceptor;
further comprising
9. The patch adjustment means adjusts the amount of toner in the main scanning direction when forming toner patches from the next time according to the printing ratio calculated by the printing ratio calculating means. The image forming apparatus according to any one of . In an image forming apparatus that forms a toner image on the surface of a photoreceptor, primarily transfers the toner image to an intermediate transfer member, and then secondarily transfers the toner image to a recording material for output, a plurality of toners are applied to the surface of the photoreceptor. A toner patch forming method for forming a toner patch between two adjacent toner images when images are continuously formed, comprising:
A plurality of toner patches having the same toner concentration are formed on the surface of the photoreceptor between at least two first adjacent toner images , and the plurality of toner patches are primarily transferred from the photoreceptor to the intermediate transfer member. a first step of switching the primary transfer rate during
a second step of detecting densities of the plurality of toner patches primarily transferred from the photoreceptor to the intermediate transfer member;
Based on the detection result in the second step, the lower limit value is set so that the density of the next and subsequent toner patches will be a toner amount that does not reduce the cleaning performance of a cleaner that removes residual toner remaining on the surface of the photoreceptor. and a third step of adjusting the amount of toner when forming subsequent toner patches so that the amount of toner is within the range of the upper limit value set so that the toner stain is not conspicuous on the back surface of the recording material; ,
A method for forming a toner patch, comprising:

Images